. . . the infants born after short intervals had a markedly high rate of mortality from all causes. Evidently some factor that is intimately connected with the short interval—perhaps through the influence of frequent births upon the mother's health—affected adversely the chances of life of the infants who followed closely after preceding births. (62, p. 445)
Eastman then went on to say:
Dr. Woodbury's monograph is a reserved and scholarly study, largely objective in character; and it contains no suggestion whatsoever as to what might be done to reduce infant mortality in the short interval groups. But those interested in the furtherance of birth control were quick to see a remedy. Certainly, they reasoned, if conception could be prevented in women during the first year or two after childbirth, the high mortality associated with the short interval could be prevented. And forthwith the Woodbury study became one of the cornerstones of the birth control movement and has remained so ever since. Upon it, indeed, is based the entire rationale, from a medical viewpoint, of so-called "child-spacing," a term which has come to be a sort of euphemism for contraception in general. . . . (62, p. 446)
Dr. Eastman's somewhat disparaging tone was prompted by the fact that his own study, which he was reporting at the time, had failed to reveal a similar association. His study will be discussed later, but students of the history of changes in attitude toward family planning on the part of the medical profession would be rewarded by reviewing the recorded comments in the discussion which followed the presentation of his report in Chicago in 1943.
Since the studies of Huse, Woodbury, and Eastman, there have been a number of further investigations of the effects of birth interval. They are as varied as the studies of family size, although fewer in number, and several of the studies previously referred to examined both variables in analyzing their data. Much of the work has been concentrated upon the fetal, perinatal (around the time of birth), infant, and early childhood mortality; there is surprisingly little data concerning the effects on the mother herself, although one might reasonably expect the "maternal depletion syndrome" mentioned earlier (14) to be aggravated by repeated short intervals as much or more than by excessive numbers of pregnancies.
In the following pages, more recent studies about the effects of birth interval will be discussed.
The Effects on Children
Birth Internal and Mortality. The association between birth interval and mortality from gestation through early childhood was examined in the retro-se two factors on increasing maternal risk are additive—eacl increases the risk independently.